Cannula having nitinol reinforced inflow region

ABSTRACT

An intravascular heart pump assembly can include a rotor with at least one impeller blade, and a cannula. The present application describes various cannulas that can be manufactured from multiple layers of material to improve flexibility, manufacturability, and durability without increasing an outer diameter of the cannula. In one embodiment, the cannula includes an inflow section having a sheet formed of a shape memory material embedded within a polymer and having at least one lateral hole or aperture in the inflow section. The at least one lateral hole is defined by a first hole in the sheet and a second hole in the outer polymer layer of the cannula. The first hole and the second hole overlap so that blood can enter the cannula through the holes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/463,156, filed Mar. 20, 2017 (now allowed). The specification of theforegoing application is hereby incorporated by reference in itsentirety.

BACKGROUND

A heart pump, such as a percutaneous intracardiac heart pump assembly,can be introduced in the heart to deliver blood from the heart into anartery. When deployed in the heart, a heart pump assembly pulls bloodfrom the left ventricle and expels the blood into the aorta, or pullsblood from the right ventricle and expels blood into the pulmonaryartery. Some heart pump assemblies pull blood through inflow aperturesinto a cannula and expel the blood from the cannula through outflowapertures.

Inflow apertures are traditionally formed of stainless-steel. They mayinclude edges that can damage the blood as it enters the cannula,causing hemolysis. Furthermore, stainless steel portions are stiff andcan be damaged by applied stresses, for example, during manufacturing,shipment, and/or when the device is being inserted into the body. Duringinsertion, for example, the heart pump can be inadvertently damaged bythe user grasping the sides of the inflow cage near the inflowapertures, deforming the cage. Accordingly, there is an opportunity forimproved cannula designs.

SUMMARY

Systems, devices, and methods described herein provide heart pumpassemblies with inflow apertures reinforced by a shape memory material.The reinforced inflow apertures are designed to prevent or reduce damageto the pump during insertion of the pump into position in the body anddamage to blood during operation of the pump. In particular, thereinforced inflow aperture portion can withstand the stress of squeezingor bending and return to an original shape after exposure to suchstress, helping the inflow holes remain open. This ability to return toshape can decrease the occurrence of inadvertent damage to blood pumpsduring insertion. The reinforced inflow apertures formed in a shapememory material portion of a heart pump can be embedded in a plasticcannula, and edges of the inflow apertures can be coated with a plasticcoating, providing a more smooth surface for blood to pass than in priorart systems.

Several advantages can be achieved by the designs disclosed herein. Forexample, embedding nitinol in a coil or sheet to reinforce the cannulabody and inflow section of the pump allows the miniaturization of theheart pump assembly for use in the heart. The reinforced inflow holesand cannula decrease the potential for damage to the heart or bloodduring use. Further, reinforced inflow holes which expose only thecannula body material to blood and tissues allow the pump to bepositioned across the aortic valve without damage to the tissues.Nitinol can be manufactured to be thinner than other commonly usedbiocompatible materials such as stainless steel, and is more flexiblefor easier use and handling.

In one aspect, an intravascular heart pump assembly includes an elongatecatheter with a proximal end to be positioned outside of a patient'sbody and a distal end to be positioned in an artery proximate to thatpatient's heart, a rotor with at least one impeller blade coupled to thedistal end of the elongate catheter, a motor operatively coupled to therotor, and a cannula. The cannula includes a cannula body having aproximal region including a proximal end and a distal region including adistal end, the proximal end coupled to the distal end of the elongatecatheter. The cannula body has a proximal region and a distal region,with the distal region including at least one lateral inflow hole andthe proximal region including at least one lateral outflow hole. Thecannula also includes a sheet formed of a shape memory material andembedded within polymer, the sheet and the polymer forming the cannulabody. In the distal region of the cannula body, the at least one lateralinflow hole is defined by a first layer having a hole in the shapememory material sheet, and by a second layer having a hole in thepolymer material, and the hole in the first layer and the hole in thesecond layer overlap along an external surface of the cannula.

In some embodiments, an outer perimeter of the hole in the second layeris within an outer perimeter of the hole in the first layer. In someembodiments, the heart pump assembly also includes at least one slittedopening in the sheet configured to allow the sheet to flex. In someembodiments, the cannula body also includes a coil formed of a shapememory material. In some implementations, at least a portion of the coilis positioned proximal to the shape memory material sheet. In someimplementations, at least a portion of the coil is positioned distal tothe shape memory material sheet.

In some embodiments, the shape memory material is nitinol. In someembodiments, the cannula body is formed of two polymer layers with thenitinol (or other shape memory material) sheet embedded between the twopolymer layers.

In some embodiments, the at least one lateral outflow hole is proximalto or aligned with the rotor. In some embodiments, the proximal regionincluding the at least one lateral outflow hole is formed from anon-memory alloy with a plurality of lateral outflow holes. In someembodiments, the proximal region including the at least one lateraloutflow hole is formed from stainless steel. In some embodiments, theheart pump assembly includes a flexible projection coupled to a distalend of the cannula. In some embodiments, the distal projection is apigtail extension.

In some embodiments, the distal region of the cannula body includes aplurality of lateral inflow holes reinforced according to any of theembodiments discussed herein. In some embodiments, the distal regionincludes a second lateral inflow hole positioned proximal to the atleast one first lateral inflow hole. In some embodiments, the cannulabody has an outer diameter less than or equal to about 22 Fr (e.g., 12Fr or 20 Fr). In some embodiments, the shape memory material sheet isless than or equal to about 0.07 mm thick. In some embodiments, a wallof the cannula body is at least 0.07 mm thick.

In another aspect, a method for producing a blood pump includes making acannula with a reinforced inflow section. In some applications, themethod includes providing a cannula body, producing a blood inflowsection by forming a first plurality of apertures and a plurality ofslits in a shape memory material sheet, rolling the shape memorymaterial sheet into a cylindrical shape, embedding the shape memorymaterial sheet in the cannula body, and forming a second plurality ofapertures through the cannula body, wherein each of the first pluralityof apertures and the second plurality of apertures fully overlap.

In some embodiments, the second plurality of apertures is formed suchthat an outer perimeter of each of the second plurality of apertures iswithin an outer perimeter of one of the first plurality of apertures. Insome embodiments, the shape memory material is formed of nitinol. Insome embodiments, embedding the shape memory material sheet in a plasticmaterial comprising the cannula body includes placing the shape memorymaterial sheet between a first polymer layer and a second polymer layer,and forming holes in the first and second polymer layers to coincidewith holes in the shape memory material sheet.

Variations and modifications will occur to those of skill in the artafter reviewing this disclosure. The disclosed features may beimplemented in any combination and subcombination (including multipledependent combinations and subcombinations), with one or more otherfeatures described herein. For example, although various specificarrangements of apertures are described herein, a heart pump assemblymay be configured to have any number of apertures arranged in anysuitable number or organization of rings. Further, the apertures mayhave any suitable size, shape, or position. The slitted holes formed inthe shape memory material sheet to allow bending and/or flexing of thecannula may also be formed in any suitable orientation and arrangementwith respect to inflow apertures. Sections of shape memory material wirecoil can be positioned proximal and/or distal of the shape memorymaterial sheet, or in some implementations may be omitted. The variousfeatures described or illustrated above, including any componentsthereof, may be combined or integrated in other systems. Moreover,certain features may be omitted or not implemented.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects and advantages will be apparent uponconsideration of the following detailed description, taken inconjunction with the accompanying drawings, in which like referencecharacters refer to like parts throughout, and in which:

FIG. 1A shows a heart pump assembly including a shape memory materialsheet;

FIG. 1B shows a heart pump assembly including an inflow section andcoil;

FIG. 2 shows a heart pump assembly including a plurality of apertures inan inflow section, according to one embodiment;

FIG. 3 shows layers of polymer material and shape memory alloy making upthe cannula body, in accordance with example implementations;

FIG. 4 shows an example pattern of apertures and slitted holes in ashape memory material sheet;

FIG. 5 shows another example pattern of apertures in a shape memorymaterial sheet;

FIG. 6 shows yet another example pattern of apertures formed in a shapememory material sheet,

FIG. 7 shows a shape memory material sheet formed into a cylindercage/basket, according to one embodiment;

FIG. 8 shows a shape memory material sheet and a shape memory materialcoil embedded in a cannula body, according to one embodiment;

FIG. 9 shows an exemplary heart pump assembly including an inflowsection inserted into a patient's heart; and

FIG. 10 shows a flow chart for a method of producing a blood inflowsection of a heart pump assembly.

DETAILED DESCRIPTION

To provide an overall understanding of the systems, methods, and devicesdescribed herein, certain illustrative embodiments will be described.Although the embodiments and features described herein are describedwith reference to specific numbers, sizes, and shapes of apertures, itwill be understood that the heart pump assembly may be configured tohave any suitable number of apertures formed in the inflow section, notlimited to the arrangements described here. Additionally, the aperturesmay have any suitable size, shape, or position. It will also beunderstood that although the distal section of the cannula assembly isreferred to as the “inflow” section, in case the blood flow direction isreversed as in a pump for supporting the right side of a patient'sheart, this section would become an “outflow” section. As will beappreciated, all embodiments described herein are applicable for bothleft and right sided heart pumps.

Systems, devices, and methods described herein provide heart pumpassemblies including a cannula with an improved inflow section. Thereinforced inflow apertures prevent trauma to blood that enters thecannula through one or more inflow apertures. In particular, the inflowapertures are formed in a shape memory sheet embedded in the cannulasuch that blood entering the cannula does not contact sharp edges withinthe aperture, but only contacts the smooth cannula material (e.g.,polymer) in which the shape memory sheet is embedded. Embedding a shapememory material sheet in a polymer material decreases potential damageto the blood, heart and other tissues, and allows miniaturization of theheart pump assembly for use in the heart. Furthermore, shape memorymaterials, such as nitinol, can be manufactured to be thinner than othercommonly used biocompatible materials such as stainless steel, allowingthe pump size to be decreased. During insertion, the pump can be subjectto squeezing forces that may damage the delicate structures near theinflow apertures if the inflow section is rigid (e.g., if it made ofnon-flexible material such as stainless steel). If a pump is damagedduring insertion, it may decrease pump efficiency or cause damage toblood and tissue. The shape memory material sheet imparts flexibility atthe inflow section and may also decrease the risk of damage to theinflow section during insertion of the pump into the introducer.

The heart pump includes a cannula body with a shape memory materialsheet forming an inflow section. For example, the sheet can be formed asan inflow cage/basket. The inflow section includes at least one firsthole formed in the shape memory material sheet, e.g., in the inflowbasket. The shape memory material sheet is embedded in a material of thecannula body, and a second hole is formed in the cannula body materialoverlapping with the first hole in the sheet to permit blood enteringthe cannula to pass through the holes without damage. The second hole inthe cannula body material may be of a smaller diameter than theconcentric first hole in the sheet, such that blood and tissues interactonly with the edges of the second hole, i.e., with edges of the inflowaperture formed from the cannula body material. The cannula body may beformed from a material which does not damage blood or tissue.Furthermore, the cannula body may comprise a polymer coated sectionextending from the pump section at a proximal end of the cannula body tothe distal end of the cannula. A shape memory material coil may also beapplied. For example a nitinol coil may be embedded within the cannulabody to reinforce the cannula body over a portion of the cannula. Theshape memory material coil also enables the cannula to flex and bendduring insertion and to return to its original shape. And further, theshape memory material coil can be positioned proximal or distal of thebasket. The use of a memory shape material sheet (and coil where used)increases the flexibility of the pump and allows the pump to retain itsshape if it is subjected to squeezing forces during insertion into thebody or into an introducer device.

FIG. 1A shows an example heart pump assembly 100 including a shapememory material sheet 113 formed as an inflow cage/basket. The heartpump assembly has a proximal end 107 coupled to an elongate catheter175, and a distal end 110, as well as a cannula 108, with cannula body109, and a rotor 102 having an impeller blade 104. The cannula body 109includes a first distal region 131 and a second proximal region 129. Thefirst distal region 131 includes a shape memory material sheet 113formed as a cylindrical inflow cage/basket embedded within a polymer,with a first lateral hole 133 formed in it. The second proximal region129 includes a second lateral hole 123. The first lateral hole 133 isdefined by a first hole 135 formed in the shape memory material sheet113 and a second hole 147 in the polymer, which overlap.

The shape memory material sheet 113 is embedded in the cannula body 109material, such that the shape memory material sheet 113 providesreinforcement of an inflow section of the cannula 108, but is notexposed to blood or tissue. The first lateral hole 133 is formed suchthat blood and tissue are protected from contacting sharp edges of theshape memory material sheet 113. The first hole 135 and the second hole147 defining the first lateral hole 133 fully overlap as shown. Forexample, the second hole 147 is formed within the first hole 135. Bloodflowing through the vasculature of a patient in the direction from thedistal end 110 to the proximal end 107 of the cannula 108 flows into thecannula body 109 through the first lateral hole 133 which functions asan inflow aperture. Blood enters the cannula body 109 at an angle suchthat if the blood comes into contact with an edge of the first lateralhole 133, it is likely to be in contact with an edge of the hole formedin the cannula body 109 material. In some implementations, the firsthole 135 and the second hole 147 may be entirely concentric, and thesecond hole 147 through the cannula body 109 is the same size or smallerthan the first hole 135. In this way, the edges that define the firstlateral hole 133 are formed from the cannula body 109 material, and thematerial of the shape memory material sheet 113 is not exposed.

FIG. 1B shows a more detailed view of the heart pump assembly 100 ofFIG. 1A, including a shape memory material sheet 113 and coil 106. Theheart pump assembly 100 includes a catheter 175, a rotor 102, a cannula108, an inflow section 116, an outflow section 124, outflow apertures127, a proximal end of the pump 107, a distal end of the pump 110, andan atraumatic tip 112. The cannula 108 has a proximal end 111, a cannulabody 109, and a distal end 157. A coil 106 is embedded in the cannulabody 109. The coil 106 extends from the outflow section 124 at theproximal end 111 to the inflow section 116. The inflow section 116 isformed of at least one lateral hole 114 in a shape memory material sheet113 embedded in the cannula body 109. The rotor 102 includes an impellerblade 104.

The rotor 102 is coupled to a distal end of the catheter 175, and isoperatively coupled to a motor (not shown). The heart pump assembly 100pulls blood through the at least one lateral inflow hole 114 in thedistal inflow section 116 and into a lumen (not shown) in the cannulabody 109. The blood is expelled through the outflow section 124 at theplurality of outflow apertures 127. The at least one lateral hole 114 isdefined by overlapping holes formed in the shape memory material sheet113 and in the cannula body 109 material (as shown in FIG. 1A). Theblood enters the cannula 108 through the at least one lateral hole 114and may contact the edge of the at least one lateral hole 114 as itenters. Blood cells may become damaged if they come into contact withsharp edges at high flow rates. The inflow section 116 formed in theshape memory material sheet 113 is embedded in the cannula body 109material in order to present only the smooth cannula body 109 materialto the blood as it enters through the at least one inflow hole 114 intothe cannula body 109, protecting the blood from damage. After enteringthe cannula body 109, the blood flows through the cannula 108 and isexpelled at the proximal end of the cannula 108 through the outflowapertures 127 at the outflow section 124. The outflow apertures 127 maybe arranged laterally about the cannula body 109 such that at least oneoutflow aperture 127 is proximal to or aligned with the rotor 102. Incase of blood flow direction reversal, the description above stillholds, but outflow section 124 would act as the inflow and inflowsection 116 would act as an outflow.

The heart pump assembly 100 may be percutaneously inserted into theheart and into the aorta. The inflow section 116 may be positioned pastthe aortic valve in the left ventricle, in order to pull blood from theleft ventricle and expel the blood into the aorta. Extending the cannula108 from the outflow section 124 to the sheet 113 embedded in thecannula body 109 such that the cannula wall is a smooth surface whicheliminates occurrence of hemolysis or tissue damage in the aortic valvesand vasculature. The at least one lateral hole 114 formed in the sheet113 in the inflow section 116 embedded in the cannula body 109 can bereinforced at the edges by the smooth material of the cannula body 109to decrease damage (e.g., hemolysis) to the blood. Atraumatic tip 112also decreases damage to the heart tissues by spacing the heart pumpassembly 100 from the heart walls. In some instances the at least onelateral hole 114 of inflow section 116 may be positioned near to thewalls of the heart or various heart structures, such as the leaflets ofthe mitral valve. The cannula body 109 material in which the sheet 113is embedded serves to soften the edges of the at least one lateral hole114 to decrease damage to these structures if they are pulled toward theat least one lateral hole 114 by the suction of the pump.

The basic configuration of FIGS. 1A and 1B may be implemented in any ofthe embodiments discussed herein. FIGS. 2-5 show various examplepatterns with which the configuration of FIGS. 1A and 1B can beimplemented. Further example patterns showing arrangements of aperturesin a wall of the cannula forming an inflow section are described in U.S.provisional application 62/382,471, the contents of which areincorporated by reference herein. FIG. 2 shows a heart pump assembly 200having a reinforced inflow section 216, according to certainembodiments. The reinforced inflow section 216 is configured as acage/basket and fitted within the heart pump assembly 200. The heartpump assembly 200 includes a rotor 202, an impeller blade 204, a cannula208 (with proximal 211 and distal 257 ends), a cannula body 209, anoutflow section 224, a plurality of outlets 227, and a distal connector205. The assembly has a longitudinal axis 225 and a distal end 210. Acoil 206 may have two coil sections 206 a and 206 b and is embedded inthe cannula body 209. The inflow section 216 is positioned in this casebetween coil sections 206 a and 206 b and includes a reinforcing sheet213 embedded in the cannula body 209. The sheet 213 includes a proximalsheet end 221 and a distal sheet end 219. A first row of holes 226 and asecond row of holes 228 are formed in the embedded sheet 213. At leastone slitted hole 222 is also formed in the embedded sheet 213 to enablethe sheet to easily bend during insertion and positioning.

The second row of holes 228 is proximal of the first row of holes 226.The first row of holes 226 and second row of holes 228 may be formed soas to extend through both the embedded sheet 213 and the cannula body209, such that the first row of holes 226 and second row of holes 228allow blood to enter the cannula 208. For example, a first hole 218 isformed through the sheet 213 and a concentric second hole 220 is formedthrough the cannula body 209. The first hole 218 is shown as beinglarger than the second hole 220, such that blood entering the cannula208 interacts only with smooth edges of the second hole 220 in thecannula body 209 and not with sharp edges of the first hole 218 formedin the shape memory sheet 213. Each aperture of the first row of holes226 and the second row of holes 228 can be aligned along thelongitudinal axis 225 of the cannula 209, or may be offset from oneanother. The at least one slitted hole 222 may be formed only in thesheet and embedded in the cannula body 209, such that it does notprovide an aperture through which blood enters the cannula 208. Instead,the at least one slitted hole 222 may allow the sheet 213 to flex orbend, for example during insertion into an introducer sheath or duringpositioning within a patient's body. The at least one slitted hole 222may be oriented to allow bending or flexing in a preferred direction.

The coil section 206 can be provided at a desired length. For example,the coil section 206 a may be 15-20 cm (e.g., 13 cm, 15 cm, 17 cm, 19cm, 20 cm, 22 cm, or 24 cm). The coil 206 (sections 206 a and 206 b)embedded in the cannula body 209 may extend from the outflow section 224to the proximal sheet end 221. The coil 206 may also extend from adistal sheet end 219 to the distal connector 205. The outflow section224 includes one or more apertures 227. The coil 206 may be joined tothe sheet 213. Alternatively, the coil 206 and sheet 213 may beunconnected except by being embedded in the cannula body 209. In thatarrangement, the coil 206 would reinforce the cannula body 209, whilethe sheet 213 would reinforce the apertures in the inflow section 216.

In some implementations, the sheet 213 is formed from a shape memorymaterial. In some implementations, the shape memory material forming thesheet 213 is principally constructed of nitinol. In someimplementations, the coil 206 also is formed from a shape memorymaterial. In some implementations, shape memory material forming thecoil 206 is principally constructed of nitinol. A coil 206 and/or sheet213 formed from nitinol or another shape memory material allowsflexibility of the cannula 208 during introduction into an introducer orpositioning in the body. For example, in some implementations the inflowsection 216 may experience substantial force when gripped and squeezedduring introduction of the pump 200 into an introducer sheath orcatheter. A cannula 208 and inflow section 216 formed of a shape memorymaterial can withstand the squeezing force and resume its original shapeafter the force has stopped. This can decrease damage to the pump duringintroduction. The coil 206 further allows flexibility of the cannulabody 209. In some implementations, the cannula body 209 is formed of abiocompatible plastic material (e.g., polyurethane). Embedding the shapememory material coil 206 and sheet 213 in the cannula body 209reinforces the cannula body 209 and the holes (for example, first row ofholes 226 and the second row of holes 228) while exposing only thecannula body 209 material to the tissue and blood of the patient.

The cannula 208 extends from proximal end 211 distal of the outflowsection 224 to the distal end 257 where the cannula body 209 is coupledto the distal connector 205. The cannula 208 includes the cage/basket ofthe inflow section 216. The cannula 208 may have an external surfacecoated by a polymer layer to present a smooth surface that does notdamage blood as it enters or passes by the cannula 208. It will beappreciated that though the cannula 208 in FIG. 2 includes a firstsection of coil 206 a, an inflow section 216 including a shape memorymaterial sheet, and a second section of coil 206 b, the cannula 208 doesnot require two coil sections and in fact in some embodiments includesno coil-reinforced sections.

Several advantages can be achieved by the designs disclosed herein. Forexample, embedding a nitinol coil 206 and sheet 213 to reinforce thecannula body 209 and inflow section 216 of the pump allows theminiaturization of the heart pump assembly 200 for use in the heart. Thereinforced holes (i.e., first row of holes 226 and second row of holes228) and cannula 208 decrease the potential for damage to the heart orblood during use. Further, reinforced holes which expose only thecannula body material to blood and tissues allow the pump to bepositioned across the aortic valve without damage to the tissues.Nitinol can be manufactured to be thinner than other commonly usedbiocompatible materials such as stainless steel, and is more flexiblefor easier use and handling.

FIG. 3 shows an illustrative view of a multilayered inflow section ofthe heart pump assembly, such as heart pump assembly 100 in FIG. 1A orFIG. 1B, or 200 in FIG. 2 , according to some implementations. Embeddinga reinforcing sheet between two layers of plastic coating ensures thatblood entering the cannula through the holes in the reinforced sectionwill encounter only the smooth edges of the plastic coating and notsharp edges of the reinforcing sheet. The inflow section (such as inflowsection 116 in FIG. 1 or 216 in FIG. 2 ) includes a layer of nitinol334, a first layer of plastic 330, a second layer of plastic 332, and anaxis 346 perpendicular to each of the layers. The layer of nitinol 334includes a first aperture 336 with a first diameter 337, a slitted hole342, and a first thickness 344. The first layer of plastic 330 has asecond aperture 338 with a second diameter 339, and has a secondthickness 343. The second layer of plastic 332 has a third aperture 340with a third diameter 341, and has a third thickness 345. The layer ofnitinol 334 is embedded between the first layer of plastic 330 and thesecond layer of plastic 332. The first aperture 336, second aperture338, and third aperture 340 are aligned along the axis perpendicular toeach of the three layers, such that the apertures overlap to create athrough hole for blood to flow into the cannula. The apertures mayoverlap entirely, as shown, such that the first aperture 336, secondaperture 338, and third aperture 340 are concentric. In someembodiments, the first aperture 336, second aperture 338, and thirdaperture 340 alternatively overlap only in portion. The first diameter337 in the first aperture 336 in the first layer of nitinol 334 islarger than the second diameter 339 of the second aperture 338 and thethird diameter 341 of the third aperture 340. The smaller seconddiameter 339 and third diameter 341 allow only the material of the firstplastic layer 330 and second plastic layer 332 to be exposed to bloodentering the cannula, keeping the blood from being damaged by sharperedges in the layer of nitinol 334.

Coating the shape memory alloy sheet on an outside portion of thecannula protects blood from being damaged by sharp edges. Coating theshape memory alloy sheet on an interior portion of the cannula similarlyprotects the blood and may also help to maintain a consistent flowpattern as the blood moves through the cannula. In some implementations,the thickness 343 of the first layer of plastic 330 and the thickness345 of the second layer of plastic 332 are approximately equal. In someimplementations, the thickness 343 of the first layer of plastic 330 isgreater than the thickness 345 of the second layer of plastic 332 Thethickness of the shape memory material sheet enables the reinforcedcannula to be bent or flexed but still maintain its shape. The totalthickness of the cannula wall includes a thickness of the nitinol (orother shape memory material) and the thickness of the polymer in whichthe nitinol is embedded. In some implementations, the layer of nitinol334 forming the shape memory material sheet is less than or equal to0.07 mm in thickness. In some implementations, the layer of nitinol 334forming the shape memory material sheet is 0.03 mm, 0.05 mm, 0.07 mm,0.09 mm, 0.1 mm, 0.2 mm, 0.25 mm or any suitable thickness. In someimplementations, the combined height of the layer of nitinol 334, firstlayer of plastic 330 and second layer of plastic 332 is 0.05 mm, 0.07mm, 0.09 mm, 0.1 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.5 mm or any suitablethickness. In some implementations, the thickness 343 of the first layerof plastic 330 is greater than the thickness 345 of the second layer ofplastic 332 and is equal to 0.03 mm, 0.04 mm, 0.05 mm, 0.08 mm, 0.1 mm,or any other suitable thickness. In some implementations, the thicknessrequired of the shape memory material sheet to withstand squeezing andbending forces during insertion may be less than a thickness that wouldbe required of a non-shape memory material to withstand similar forces.The layers of shape memory material and plastic layers do notsubstantially increase a thickness of the cannula body wall as comparedto the wire-reinforced cannula without the shape memory sheet.

In some implementations, the first layer of plastic 330 faces aninterior of the cannula body. In some implementations, the second layerof plastic 332 faces an interior of a cannula body. In someimplementations, an edge of the aperture 338 in the first plastic layer330 and/or an edge of the aperture 340 in the second plastic layer 332is rounded, beveled, or chamfered. In some implementations, the entiretyof an edge of the first aperture 336 is embedded in the material of thefirst plastic layer 330 and the second plastic layer 332. In someimplementations, the edge of the first aperture 336 is embedded in thematerial of the first plastic layer 330 and the second plastic layer332. For example, a proximal edge of the first aperture 336 may be fullyembedded in the material of the first plastic layer 330 and the secondplastic layer 332 forming a smooth surface that prevents damage to bloodentering the cannula.

The slitted hole 342 formed in the layer of nitinol 334 may be formed inany shape. The slitted hole 342 may be formed as an oblong slit whichmay be oriented to allow preferential bending or flexing of the cannulain a particular direction. The slitted hole 342 is formed in the layerof nitinol 334, but no corresponding aperture is formed in the firstplastic layer 330 and the second plastic layer 332. Because of this, noblood enters the cannula through the slitted hole 342, but the slittedhole 342 serves to increase the flexibility of the cannula and allowsbending and flexing of the cannula at the nitinol sheet.

In general, the reinforced inflow section embedded in the cannula bodyas shown in FIGS. 1A, 1B, and 2 , can be constructed with holes arrangedin any orientation. The slitted holes are added to the reinforcing sheetto allow the cannula to bend at the inflow section, enabling positioningof the cannula within the vasculature. The slitted holes may be producedto enable the inflow section to bend in particular directions toaccommodate the bends required to position the cannula in a particularposition within the heart. Alternatively, the slitted holes may beproduced to enable the inflow section to withstand squeezing forcesduring insertion of the cannula, enabling the inflow section to bedeformed and to resume the original shape without damage to the inflowholes. FIGS. 4-7 illustrate example arrangements of inflow holes andslitted holes to accomplish these outcomes.

FIG. 4 shows a pattern of inflow apertures and slitted holes in a shapememory material sheet 413, in accordance with some implementations.Shape memory material sheet 413 (which can be coiled or rolled into acage/basket formation and embedded within a cannula) includes a distaledge of the sheet 419, a proximal edge of the sheet 421, a firstplurality of inflow apertures 448, a second plurality of inflowapertures 450, a first plurality of slitted holes 451 and a secondplurality of slitted holes 452. The first plurality of inflow apertures448 and the second plurality of inflow apertures 450 are formed as holesthrough the shape memory material sheet and covering cannula bodymaterial. In particular, apertures in the first plurality of inflowapertures 448 are formed from first aperture 458 a-d of the shape memorymaterial sheet, and from second aperture 460 a-d of the cannula bodymaterial in which the shape memory material sheet is embedded. The firstplurality of slitted holes 451 and the second plurality of slitted holes452 are formed only in the shape memory material sheet 413.

The second plurality of inflow apertures 450 is proximal of the firstplurality of inflow apertures 448. The first plurality of inflowapertures 448 and the second plurality of inflow apertures 450 may beoffset from each other along an axis 461 running from a proximal edge ofthe sheet 421 to a distal end of the sheet 419. For example, aperture460 b is offset from aperture 464 b. The first plurality of inflowapertures 448 and the second plurality of inflow apertures 450 may bealigned with one or more of the holes in the first plurality of slittedholes 451 and a second plurality of slitted holes 452. For example,aperture 460 b is aligned with slitted hole 466 b along axis 461, andaperture 464 c is aligned with slitted hole 468 b along axis 463.Alignment of apertures with slitted holes allows the cannula to flex ina position proximal to the apertures allowing the inflow section to bedeformed during positioning of the cannula, while maintaining sufficientrigidity and reinforcement of the apertures.

Though the first plurality of inflow apertures 448 and second pluralityof inflow apertures 450 are defined by holes through the sheet 413overlapping holes in the cannula body, the area of the holes is suchthat the flow rate of blood through the cannula is maintained. In someimplementations, the first plurality of inflow apertures 448 may includeapertures 460 a-d having a larger area than apertures 464 a-d of thesecond plurality of inflow apertures 450. The area of the apertures 460a-d of the first plurality of inflow apertures 448 may be less than 20mm². In some implementations, the area of apertures 460 a-d of the firstplurality of inflow apertures 448 is 0.5 mm², 1 mm², 5 mm², 10 mm², 15mm², 18 mm², 20 mm², 23 mm², 25 mm² or any other suitable area. The areaof apertures 464 a-d of the second plurality of inflow apertures 450 maybe less than 12 mm². In some implementations, the area of apertures 464a-d of the second plurality of inflow apertures 450 may be 0.25 mm², 0.5mm², 1 mm², 2 mm², 5 mm², 10 mm², 12 mm², or any other suitable area.The area of the apertures of the first plurality of inflow apertures 448and the second plurality of inflow apertures 450 may be chosen tosupport a particular flow rate or flow pattern of blood into thecannula.

In some implementations, a large portion of blood that enters thecannula body enters through the most proximal of the plurality ofapertures (e.g., the second plurality of inflow apertures 450), forexample through the apertures 464 a-d. Variations in the number and sizeof the apertures in the distal end portion can alter the flowdistribution of blood into the cannula. All arrangements in FIGS. 4-6show the plurality of apertures disposed on a similar portion of thedistal end portion of the cannula (as shown in FIG. 1 A, 1B, or 2), butthe apertures vary in the shape, positioning, and relative size.

While FIG. 4 shows inflow apertures aligned with slitted holes in ashape memory material sheet, FIG. 5 shows a shape memory material sheet513 having a pattern of inflow apertures with slitted holes set inbetween, in accordance with some implementations. The shape memorymaterial sheet includes a distal edge 519, a proximal edge 521, a firstplurality of inflow apertures 548, a second plurality of inflowapertures 550, a first plurality of slitted holes 551, a secondplurality of slitted holes 552, a third plurality of slitted holes 553,a fourth plurality of slitted holes 554, a fifth plurality of slittedholes 555, and a sixth plurality of slitted holes 556. Apertures in thefirst plurality of inflow apertures 548 are formed from first apertures558 a-d formed in the shape memory material sheet and from secondapertures 560 a-d formed in the cannula body material in which the shapememory material sheet is embedded. Inflow apertures in the secondplurality of inflow apertures 550 are formed from third apertures 562a-d formed in the shape memory material sheet and from fourth apertures564 a-d formed in the cannula body material.

The first plurality of inflow apertures 548 and the second plurality ofinflow apertures 550 are aligned along an axis 561 running from aproximal edge of the sheet 521 to a distal end of the sheet 519. One ormore of the slitted holes may also be aligned with the inflow aperturesof the first plurality of inflow apertures 548 and the second pluralityof inflow apertures 550. For example, aperture 560 b and aperture 562 bare aligned with a slitted hole of the plurality of slitted holes 555.Other slitted holes are interspersed between each of the first pluralityof inflow apertures 548, for example, slitted holes of the firstplurality of slitted holes 551, the second plurality of slitted holes552, and the third plurality of slitted holes 553 are interspersedbetween the apertures 560 a-d of the first plurality of inflow apertures548. Interspersing slitted holes between the apertures of the firstplurality of inflow apertures 548 increases the flexibility of thecannula and inflow section in the region of the apertures. This mayprevent damage to the apertures during insertion of the cannula into anintroducer sheath or into the vasculature of a patient. The increasedflexibility of the inflow section in the region of the apertures mayalso assist in the placement of the cannula without damage to hearttissues.

FIG. 6 shows a pattern of inflow apertures formed in a shape memorymaterial sheet 613, in accordance with some implementations. Shapememory material sheet 613 includes a distal edge 619, a proximal edge621, a first plurality of inflow apertures 648, a second plurality ofinflow apertures 650, a first plurality of slitted holes 651, a secondplurality of slitted holes 652, a third plurality of slitted holes 653,a fourth plurality of slitted holes 654, a fifth plurality of slittedholes 655, and a sixth plurality of slitted holes 656. Apertures in thefirst plurality of inflow apertures 648 are formed from first apertures658 a-d formed in the shape memory material sheet, and from secondapertures 660 a-d formed in the cannula body material in which the shapememory material sheet is embedded. Inflow apertures in the secondplurality of inflow apertures 650 are formed from third apertures 662 aand 662 b formed in the shape memory material sheet, and from fourthapertures 664 a and 664 b formed in the cannula body.

In some implementations, the shape memory material sheet 613 is formedfrom a nitinol sheet. After the apertures and slitted holes (forexample, first apertures 658 a-c, third apertures 662 a and 662 b, firstplurality of slitted holes 651, a second plurality of slitted holes 652,a third plurality of slitted holes 653, a fourth plurality of slittedholes 654, a fifth plurality of slitted holes 655, and a sixth pluralityof slitted holes 656) are formed in the shape memory material sheet 613,shape memory second apertures 660 a-c and fourth apertures 664 a and 664b may be formed in the cannula body material to coincide with theapertures 658 a-c and 662 a-b. Alternatively, the shape memory materialsheet 613 can be joined to the cannula, such as to a nitinol coil beforebeing embedded in the material of the cannula body.

FIG. 7 shows a shape memory material sheet (such as the memory materialsheet 413 of FIG. 4 , the memory material sheet 513 of FIG. 5 , or theshape memory material sheet 613 of FIG. 6 ) formed into a cylinder 701cage/basket. Cylinder 701 includes a shape memory material sheet 713, adistal end of the sheet 719, a proximal end of the sheet 721, a firstplurality of inflow apertures 748, a second plurality of inflowapertures 750, and slitted holes 772 and slitted holes 771. The shapememory material sheet 713 is curved to form a cylinder such that eachside edge of the memory material sheet 713 meets or approaches edge 770.The distal end of the sheet 719 and proximal end of the sheet 721 formthe ends of the cylinder to which the shape memory coil may be attached.

FIG. 8 shows a shape memory material sheet 813 and a shape memorymaterial coil 806 embedded in a cannula body 809, in accordance withsome implementations. Shape memory material sheet 813 includes an inflowsection 816, at least one inflow aperture 814, at least one slitted hole822, a distal end of the sheet 819 and a proximal end of the sheet 821.The cannula body 809 includes a coil 806, a proximal end of the cannula811, and a distal end of the cannula body 857. The shape memory materialsheet 813 is coupled to the coil 806 comprising the cannula body 809 at815. The shape memory material sheet 813 is coupled at the distal end ofthe sheet 819 to a distal section 817 of the pump assembly. The distalsection 817 may include an additional section of coil, such as coil 806.Alternatively or additionally, the distal section 817 may include anadditional section of solid material, such as a section of stainlesssteel.

In some implementations, coil section 806 is joined to shape memorymaterial sheet 813, forming a unitary shaped metal structure thatstabilizes the cannula and openings. For example, the coil section 806may be welded to the shape memory material sheet 813. In someimplementations, coil section 806 and shape memory material sheet 849are not joined but are embedded in the cannula body 809 material andtherefore stabilize the cannula. Cannula body 809 may be formed of aplastic material such as polyurethane.

FIG. 9 shows a heart pump assembly 900 located in a heart 903 of apatient. The heart 903 includes a left ventricle 982, aorta 976, andaortic valve 978. The heart pump assembly 900 includes a catheter 975, amotor housing 905, an outflow section 924, a cannula body 909, a coil906, an inflow section 916, a shape memory material sheet 913, at leastone inflow aperture 914 formed as a hole in the shape memory materialsheet 913, a distal end of the cannula 910, and a flexible projection912. The motor housing 905 is coupled at its proximal end to thecatheter 975 and at its distal end to the cannula body 909. The motor905 also drives a rotor (not visible in figure) which rotates to pumpblood from the inflow section 916 through the cannula body 909 to theoutflow section 924. Arrow 984 shows the direction of the blood as itenters the cannula body 909 at the inflow section 916, while arrow 986shows the direction of the blood as it exits the cannula body 909 at theoutflow section 924 into the aorta 976. The cannula body 909 ispositioned across the aortic valve 978 such that the inflow section 916is located within the left ventricle 982 and the outflow section 924 islocated within the aorta 976. This configuration allows the heart pumpassembly 900 to pump blood from the left ventricle 982 into the aorta976 to support cardiac output. It will be appreciated that the pump 900may be applicable as a left-side support device as shown, or may equallybe used as a right-sided heart pump. In right-side support embodiments,the blood flow direction is reversed and the inflow section 916 willfunction as an outflow, and the outflow section 924 will function as aninflow.

The coil 906 and shape memory material sheet 913 increase theflexibility of the heart pump assembly 900, allowing it to be easilyinserted into position in the heart 903. In some implementations, heartpump assembly 900 is first inserted into an introducer sheath (notshown). Insertion of the heart pump assembly 900 into a sheath mayrequire a technician or health care professional to handle the heartpump assembly 900 and potentially to exert squeezing forces on variousportions of the heart pump assembly 900. The shape memory material sheet913 forming the inflow section 916 can withstand such squeezing forcesand return to its intended shape even after being subjected to suchforces. In some implementations, the outflow section 924 is formed froma non-memory material or alloy. For example, the outflow section 924 maybe formed from stainless steel.

In some instances, the positioning of the heart pump assembly 900 placesthe inflow section 916 and the at least one inflow aperture 914 nearvalve leaflets or other heart tissues. This may be due to the individualanatomy of the particular heart 903. The walls or tissues of the heart903 can be sucked by the suction of the pump towards the inflow section916 and may become suctioned to the at least one inflow aperture 914,which may damage the tissues of the heart. Embedding the coil 906 andthe shape memory material sheet 913 in the material of the cannula body909 provides a pathway for blood to enter the cannula such that itencounters the smooth edges of the cannula body 909 material rather thansharp edges of the shape memory material sheet 913. Sharp edges of theshape memory material sheet 913 are embedded in the smooth cannula body909 material, further protecting the heart tissues and leaflets frombeing damaged by sharp edges if the tissues are suctioned to an inflowaperture.

The heart pump assembly 900 pumps blood from the left ventricle into theaorta in parallel with the native cardiac output of the heart 903. Theblood flow through a healthy heart is typically about 5 liters/minute,and the blood flow through the heart pump assembly 900 can be a similaror different flow rate. For example, the flow rate through the heartpump assembly 900 can be 0.5 liters/minute, 1 liter/minute, 1.5 litersper minute, 2 liters/minute, 2.5 liters/minute, 3 liters/minute, 3.5liters/minute, 4 liters/minute, 4.5 liters/minute, 5 liters/minute,greater than 5 liters/minute or any other suitable flow rate.

The motor housing 905 of the heart pump assembly 900 is connected to amotor (not shown). The motor is internal to and integrated with themotor housing 905. In other implementations the motor is external to thebody and connected to the pump via a drive shaft (not shown) within acatheter 975 and in such an example the heart pump assembly 900 may notinclude the motor housing 905. The cannula body 909 is connected to adistal end of the motor housing 905 at the outflow section 924.

The heart pump assembly 900 can be inserted in various ways, such as bypercutaneous insertion into the heart 903. For example, theintravascular heart pump system can be inserted through a femoral artery(not shown), through the aorta 976, across the aortic valve 978, andinto the left ventricle 982. In certain implementations, the heart pumpassembly 900 is surgically inserted into the heart 903. In someimplementations, the heart pump assembly 900, or a similar systemadapted for the right heart, is inserted into the right heart. Forexample, a right heart pump similar to the heart pump assembly 900 canbe inserted through the pulmonary vein, bypassing the right atrium andright ventricle, and extending into the pulmonary artery. In certainimplementations, the heart pump assembly 900 may be positioned foroperation in the vascular system outside of the heart 903 (e.g., in theaorta 976). By residing minimally invasively within the vascular system,the heart pump assembly 900 is sufficiently sensitive to allowcharacterization of native cardiac function.

In some implementations, the heart pump assembly 900 may be sized to fitthe heart of a patient. In some implementations, the cannula body 909has a length of about 17 cm. In some implementations, the cannula bodyhas a length of 11 cm, 12 cm, 15 cm, 17 cm, 19 cm, 20 cm, 22 cm or anyother suitable length. In some implementations, the cannula body 909 hasan outer diameter of less than or equal to about 22 Fr. In someimplementations, the cannula body 909 has an outer diameter of 17 Fr, 19Fr, 22 Fr, 24 Fr, or any other suitable diameter.

The flexible projection 912 is coupled to a distal end of the cannula910, and is distal of the inflow section 916 of the heart pump assembly900. The flexible projection 912 spaces the cannula body 906 from thewalls of the heart 903 and prevents the at least one inflow aperture 914in the inflow section 916 from suctioning to the walls of the heart 903.The flexible projection 912 may be a pigtail extension. As will beappreciated, such a device can include any of the configurations ofapertures described above. The device may or may not include anatraumatic tip or flexible distal projection 912.

FIG. 10 shows a flow chart for a method of producing a blood inflowsection (e.g., inflow section 116 of FIG. 1B, 216 of FIG. 2, 916 of FIG.9 , or any other suitable inflow section) of a heart pump assembly. Themethod 1000 may be implemented to form an inflow section from a shapememory material sheet having a plurality of apertures formed therein. Instep 1002 a plurality of inflow apertures and a plurality of slits areformed in a shape memory material sheet. The apertures may be all thesame size and shape, or may be a variety of sizes and/or shapes. Theapertures may be formed in any number or pattern and may be any suitableshape, such as a circle, an oblong shape, a tear drop shape. Theapertures may be aligned along an axis or may be offset from oneanother. The shape memory material sheet may be nitinol. In someimplementations, the shape memory material sheet is 0.07 mm inthickness. In some implementations, the shape memory material sheet hasa thickness less than or equal to 0.03 mm, 0.05 mm, 0.07 mm, 0.09 mm,0.1 mm, 0.2 mm, 0.25 mm or any other suitable thickness.

As with the plurality of apertures, the plurality of slits may all bethe same size and shape or they may be a variety of sizes and/or shapesof a configuration designed to enable the pump to flex. The plurality ofslits may be oblong in a uniform direction on the shape memory materialsheet. The slits may be arranged between the plurality of apertures,and/or may be proximal or distal to the apertures. The holes provideincreased flexibility of the shape memory material in the region of theholes.

At step 1004, the shape memory material sheet is rolled or formed into acylindrical shape. The rolled shape memory material sheet forms theinflow section or inflow cage/basket of the cannula body. The shapememory material sheet is curved to form a cylinder such that a firstside edge of the memory material sheet meets or approaches a secondopposite side edge. The distal end of the sheet and proximal end of thesheet form the ends of the cylinder to which the shape memory coil maybe attached.

At step 1006, the shape memory material sheet is embedded in a cannulabody material. The cannula body material may be a plastic material, suchas polyurethane, or any other suitable plastic. Embedding the shapememory material sheet in the cannula body material may include embeddingthe shape memory material sheet between a first layer of the cannulabody material and a second layer of the cannula body material. In someimplementations, the embedded shape memory material sheet and cannulabody material has a thickness of 0.05 mm, 0.07 mm, 0.09 mm, 0.1 mm, 0.2mm, 0.25 mm, 0.3 mm, 0.5 mm or any suitable thickness.

At step 1008, a second plurality of apertures is formed in the cannulabody material such that each of the first plurality of apertures andeach of the second plurality of apertures overlay. In someimplementations, an outer perimeter of each of the second plurality ofapertures is within an outer perimeter of one of the first plurality ofapertures. In some implementations, the outer perimeter of each of thesecond plurality of apertures extends beyond the outer perimeter of eachof the first plurality of apertures by 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5mm, or any suitable distance. In some implementations, the firstplurality of apertures and the second plurality of apertures are thesame or a similar shape. In some implementations, the first plurality ofapertures and the second plurality of apertures have substantiallydifferent shapes. In some implementations, the first plurality ofapertures and the second plurality of apertures are formedsimultaneously.

In some implementations, an edge of each of the second plurality ofapertures is rounded, beveled, or chamfered. In some implementations,the entirety of the edge of each aperture in the shape memory materialsheet forming is embedded in the polymer cannula body. In someimplementations, only a portion of the edge of each aperture in theshape memory material sheet is embedded in the cannula body material.For example, a proximal edge of the shape memory material sheetforming/surrounding a first aperture may be fully embedded in thepolymer cannula body material forming a smooth surface that preventsdamage to blood entering the cannula.

The foregoing is merely illustrative of the principles of thedisclosure, and the apparatuses can be practiced by other than thedescribed embodiments, which are presented for purposes of illustrationand not of limitation. It is to be understood that the apparatusesdisclosed herein, while shown for use in percutaneous heart pumps, maybe applied to apparatuses in other applications requiring reinforcementof section subject to squeezing forces while maintaining a clearaperture for inflow.

Variations and modifications will occur to those of skill in the artafter reviewing this disclosure. The disclosed features may beimplemented, in any combination and subcombination (including multipledependent combinations and subcombinations), with one or more otherfeatures described herein. The various features described or illustratedabove, including any components thereof, may be combined or integratedin other systems. Moreover, certain features may be omitted or notimplemented.

Examples of changes, substitutions, and alterations are ascertainable byone skilled in the art and could be made without departing from thescope of the information disclosed herein. All references cited hereinare incorporated by reference in their entirety and made part of thisapplication.

I claim:
 1. A method for producing a blood inflow section, comprising:forming a first plurality of apertures and a plurality of slits in ashape memory material sheet; rolling the shape memory material sheetinto a cylindrical shape; embedding the shape memory material sheet in apolymer material to form a cannula body; and forming a second pluralityof apertures through the cannula body, wherein each of the firstplurality of apertures and the second plurality of apertures overlay;wherein embedding the shape memory material sheet in a polymer materialcomprises embedding the shape memory material sheet between a firstpolymer layer and a second polymer layer.
 2. The method of claim 1,wherein an outer perimeter of each of the second plurality of aperturesis within an outer perimeter of one of the first plurality of apertures.3. The method of claim 2, wherein the shape memory material sheet isformed of nitinol.
 4. The method of claim 1, wherein an outer perimeterof each of the second plurality of apertures extends beyond an outerperimeter of each of the first plurality of apertures by at least 0.5mm.
 5. The method of claim 1, wherein the first plurality of aperturesand the second plurality of apertures are of the same shape.
 6. Themethod of claim 1, wherein the first plurality or apertures and thesecond plurality of apertures have substantially different shapes. 7.The method of claim 1, wherein the first plurality of apertures and thesecond plurality of apertures are formed simultaneously.
 8. The methodof claim 1, wherein an edge of each of the second plurality of aperturesis any one of: rounded, beveled, or chamfered.
 9. The method of claim 1,wherein at least a portion of an edge of each of the second plurality ofapertures is embedded in the cannula body material.
 10. The method ofclaim 1, wherein the cannula body has an outer diameter of less than orequal to about 22 Fr.
 11. The method of claim 1, wherein the memorymaterial sheer is less than or equal to 0.07 mm thick.